3GPP Long Term Evolution, LTE, is the fourth-generation mobile communication technologies standard developed within the 3rd Generation Partnership Project, 3GPP, to improve the Universal Mobile Telecommunication System, UMTS, standard to cope with future requirements in terms of improved services such as higher data rates, improved efficiency, and lowered costs. The Universal Terrestrial Radio Access Network, UTRAN, is the radio access network of a UMTS and Evolved UTRAN, E-UTRAN, is the radio access network of an LTE system. In an UTRAN and an E-UTRAN, a User Equipment, UE, is wirelessly connected to a radio access node, commonly referred to as a NodeB, NB, in UMTS, and as an evolved NodeB, eNodeB or eNodeB, in LTE. A radio access node is a general term for a radio network node capable of scheduling transmission to and from user equipment and transmitting radio signals to a UE and receiving signals transmitted from a UE.
In 3GPP systems, user equipment is allowed to attach to and access a wireless communication network if the user equipment is associated with a subscription that allows the wireless communication network to authenticate the user equipment.
Today user equipments, such as mobile phones, typically support other wireless technologies such as Wireless Local Area Networks, commonly referred to as WLAN, in addition to the cellular standards. As a means to improve the network capacity in future networks, WLAN is intended to be an integral part. That is, WLAN will be regarded as just another radio access technology, so that handover can be made to WLAN without the user noticing that the service is no longer being carried by 3GPP technologies like WCDMA or LTE.
Mobile operators are today mainly using WLAN to offload traffic from the mobile networks but the opportunity to improve end user experience regarding performance is also becoming more important. The current WLAN deployments are basically totally separate from mobile networks, and are to be seen as non-integrated. The usage of WLAN is increasing due to the free and wide unlicensed spectrum, and the increased availability of WLAN in mobile terminals like smart phones and tablets. The end users are also becoming more and more at ease with using WLAN for example at offices and homes.
Presently, handover to, or access selection of, the WLAN radio access network is controlled by the user equipment, rather than by the network, due to that the WLAN network is still not sufficiently tightly integrated with the cellular networks using 3GPP technologies. However, using WLAN is often preferred from a user perspective, because of the lower cost associated with it. Therefore, a handover is often performed to WLAN as soon as a WLAN network is detected and the signal strength is sufficiently high. Hence, when user equipment is in range of a WLAN network it will typically connect to this wireless network when the received signal strength indication, RSSI, is sufficiently high, without further analysis.
WLAN integration towards the mobile core network is emerging as a good way to improve the end user experience further. These solutions consist mainly of a common authentication between 3GPP and WLAN, and an integration of WLAN user plane traffic to the mobile core network. The common authentication is based on automatic SIM-based authentication in both access types. The WLAN user plane integration provides the mobile operator the opportunity to provide the same services, like parental control and subscription based payment methods, for the end users when connected both via 3GPP and via WLAN.
WLAN integration into Radio Access Network, RAN, is also emerging as an interesting study object. There are basically two different possible level of integration that could be implemented either separately or together. A first level of integration is to combine both 3GPP and WLAN in the small pico-base stations to gain access to the WLAN sites with 3GPP technology and vice versa. The second level of integration is to integrate the WLAN access tighter into the RAN by introducing enhanced network controlled traffic steering between 3GPP and WLAN based on knowledge about the total situation on the different accesses.
A reason for this second level of integration is to avoid potential issues with UE controlled WLAN selection such as selecting WLAN when the WLAN connection is bad or when the UE is moving, thus giving better end user performance and better utilization of the combined WLAN and cellular radio network resources.
In order to achieve this functionality it is required to link or connect the UE context in the 3GPP RAN, which holds information e.g. about radio performance and UE mobility on the 3GPP side, with the UE context in the WLAN network. This can then enable a network entity to take decisions whether the UE should access the WLAN network or not depending e.g. on if the UE is stationary, and/or has a good connection to the WLAN AP. The decision can then be signaled to the UE or executed internally in the 3GPP/WLAN network, e.g. to control UE admission to WLAN.